Journal of Physical Chemistry A, Vol.111, No.29, 6813-6821, 2007
Photoelectron imaging of atomic iodine following a-band photolysis of CH3I
Photoionization of the iodine atom following methyl iodide A-band photodissociation was studied over the wavelength range of 245.5-261.6 nm by photoelectron imaging technique. Final state-specific speed and angular distributions of the photoelectron were recorded. Two types of the photoelectron resulted from ionizing the I atom from the photodissociation of CH3I were identified: (a) (2 + 1) REMPI of the ground state I atom, and (b) two-photon excitation of spin-orbit excited I(P-2(1/2)) to autoionizing resonances converging to the P-3(1) state of I+. In addition, some weaker signals were attributed to one-photon ionization of I atoms produced in some higher excited states from multiphoton ionization of CH3I followed by dissociation. Analysis of relative branching ratios to different levels of I+ (in case a) revealed that the final ion level distributions are generally dominated by the preservation of the ion-core configuration of the intermediate resonant state. A qualitative interpretation of the electron angular distribution from an autoionization process is also given.